Question about 2F intake manifold taper screw plug (1 Viewer)

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Hello fellow MUDders, I am putting together a 2F for my 60 with scraped up parts and have a question about the 2F intake manifold's taper screw plug, pictured here:


1643571793029.png


A previous owner of the intake manifold I have crossthreaded the hole the taper screw plug goes into and I want to chase the threads with a thread chaser since the plug will only go in about halfway now.

I was wondering if anyone knew if this screw plug was BPST or NPT and its threads per inch? I measured with the caliper and it looks like its 41/64" in diameter:

1643572133846.png
1643574182697.png


The threads did not match either the 1.25 metric or the 18 or 20 SAE threads on my thread gauge, and I don't have a BSPT/NPT thread gauge to confirm if the taper plug screw's tpi might be within either of those standards. It looks like BSPT has a 19 tpi standard but then it also comes in 1/4" per foot taper and 3/4" per foot taper and I wouldnt know how to determine the per foot taper of this taper screw plug.

Here is how the plug measures against 18 tpi on the SAE thread gauge leaf:
1643574367606.png


And here is a photo of the crossthreads some other bonehead besides myself put into the intake that won't allow the plug to screw in but half-way:

1643574490554.png


If anyone could help me with information about what this taper screw plug and hole's size is so I can chase the thread appropriately, I would be so grateful and willing to pay the customary MUD fee of beers. I am hesitant to continue putting more parts on the engine until I address this as I don't want to end up having to disassemble it to take the manifolds back to the machine shop.

Also, if anyone may know what the best thread sealer to use on this application might be, that would be awesome if shared with me as well. I imagine the intake has to have a good vacuum and thus all ports that should be sealed should seal airtight.

Thanks to all who take a moment to share their thoughts and wisdom.


Here is the engine in progress:

1643575023431.png
 

OSS

SILVER Star
Joined
Jun 30, 2017
Messages
4,712
Location
Oblivion
For future reference, Toyota uses Metric on everything they make. They don’t have anything that uses NPT threads. If there’s a tapered hole in metal — it’s BSPT.
While I don’t know the size of that plug, I know what a LC machine shop would use for a sealant: Permatex Ultra Copper RTV.
They used that stuff on a plug in the exhaust manifold which gets way hotter than the intake manifold.

514622D6-3D4D-487C-9657-66A5C4200945.jpeg
 

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Thank you @OSS I figured it must be metric but the thread didn't match any of the metric leaves in my thread pitch gauge, and, yes the hex is a metric size 8, but I was thrown off by the 16.4mm measure I got with the caliper. I appreciate the sealer information. I'll have to get that for when I get the plug fitted correctly.

@Spike Strip , this is on the intake manifold, not the one I bought from you, which was the exhaust manifold. Exhaust manifold is excellent. The intake came with the engine block, which came with both a cracked head and a cracked exhaust. I am wondering if this cross threaded hole lead to the original engine owner's engine running lean on account of not being airtight and causing some kind of malfunction that caused the head and exhaust that were originally on the block to crack. If that's the case, that's all the more reason why I don't want to run a cross threaded screw plug in here.

Another thing I just considered is whether I could make this a vacuum meter port to monitor engine vacuum through and have a meter mounted in the dash. If the manifolds have to come back off for rethreading of that hole, I thought maybe an upgrade in function to serve as a vacuum gauge port would work too. Any thoughts on this?
 

Spike Strip

Goblin Mode Activated
SILVER Star
Joined
Nov 22, 2005
Messages
16,280
Location
Lost Angeles
Oh yeah - It was just the Exh manifold. Forgot.

Anyway, I'm not sure, but I think all BSP is Imperial. I'm not 100% on that, but pretty sure there's no such thing as Metric BSP thread.

Have you torqued down the manifold?

That plug is steel, and the Intake is obviously softer Aluminum. I think you should be able to slather some sealant on the plug and make sure you start it perfectly square, and it should cut or straighten the threads until you reach the good section. That plug is available from Toyota for a couple bucks, you could take the old one and make some perpendicular cuts (to the thread) in it and kind of use it as a thread chaser ?

Personally, this is my favorite thread sealer, though the orange RTV is probably OK, but I don't think RTV does well in contact with gasoline. That plug comes from the factory with locking/sealing compound on it.

Maybe @ToyotaMatt knows the size?


1643604326584.png
 

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
UOTE="Spike Strip, post: 14280747, member: 9610"]
Oh yeah - It was just the Exh manifold. Forgot.

Anyway, I'm not sure, but I think all BSP is Imperial. I'm not 100% on that, but pretty sure there's no such thing as Metric BSP thread.

Have you torqued down the manifold?

That plug is steel, and the Intake is obviously softer Aluminum. I think you should be able to slather some sealant on the plug and make sure you start it perfectly square, and it should cut or straighten the threads until you reach the good section. That plug is available from Toyota for a couple bucks, you could take the old one and make some perpendicular cuts (to the thread) in it and kind of use it as a thread chaser ?

Personally, this is my favorite thread sealer, though the orange RTV is probably OK, but I don't think RTV does well in contact with gasoline. That plug comes from the factory with locking/sealing compound on it.

Maybe @ToyotaMatt knows the size?


View attachment 2909965
[/QUOTE]
Thank you for that suggestion for making a thread chaser out of the old screw plug. I'll Dremel some perpendicular notches in the screw once I get the new one. I did torque the manifolds on already, so I kinda wanted to keep them on, but if need be, I'll take them off and get a new gasket. I think a sealed hole is critical in this location given the history of the engine. I'll get the sealant you posted as well. Any thoughts on using the hole for a vacuum gauge port or should I just keep it simple and be glad if I get the hole to seal properly? Thank you!
 

Spike Strip

Goblin Mode Activated
SILVER Star
Joined
Nov 22, 2005
Messages
16,280
Location
Lost Angeles
That port would be fine as a Vacuum gauge port, providing you can find a appropriate fitting.

I'm not 100% on this either, but I did at one point look into if Toyota had a vacuum port that might fit that spot and came up with this:

90404-51010​

Union

But I never went ahead and ordered one to see if it was the right size.

You wanna be the tester ? ;) 🤷‍♀️

1643606556407.png
 

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
That port would be fine as a Vacuum gauge port, providing you can find a appropriate fitting.

I'm not 100% on this either, but I did at one point look into if Toyota had a vacuum port that might fit that spot and came up with this:

90404-51010​

Union

But I never went ahead and ordered one to see if it was the right size.

You wanna be the tester ? ;) 🤷‍♀️

View attachment 2910009
Thank you for this research. A little while ago this evening I came across this thread in the 40/55 tech forum with a similar part:


"Union (For Front Drive Shift) - Part Number 90404-51093"

Credit to @4Cruisers on that thread.

I'll look into these and compare to just going with the screw plug. Sometimes it's hard to decide between increasing functionality and just leaving good enough alone.
 

Godwin

Resident Herpetologist
SILVER Star
Joined
Dec 4, 2004
Messages
6,216
Location
Alabama
Thank you for this research. A little while ago this evening I came across this thread in the 40/55 tech forum with a similar part:


"Union (For Front Drive Shift) - Part Number 90404-51093"

Credit to @4Cruisers on that thread.

I'll look into these and compare to just going with the screw plug. Sometimes it's hard to decide between increasing functionality and just leaving good enough alone.

Considering that you'll have to retap whether to replug the holes or add a port for a vacuum gauge I suggest use this spot for the vacuum gauge connection.
 

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Considering that you'll have to retap whether to replug the holes or add a port for a vacuum gauge I suggest use this spot for the vacuum gauge connection.
I'm leaning in this direction @Godwin I like the idea of a dashboard of all the information I can get on the engine while I'm driving. I think it would help with any issues that might come up later too like diagnosing, tune-up, etc. Just want to see what parts would be needed and ask others with this set up what their experience has been.
 

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Mcmaster-carr has some nice drawings for most of their hardware. Below is an example for 1/4" BSPT (british standard pipe taper) plug. Elsewhere I found a table showing that the thread pitch for 1/4" BSPT is 19TPI (see link). There is also a BSPP (British standard pipe parallel) which has parallel threads.

View attachment 2910142


Thanks for this @2mbb I think the 19 tpi is probably what the Toyota screw plug is too. I also found this article online Fitting Connection Types: British, German & Japanese - https://blog.brennaninc.com/connection-types-british-connections that talks about how BSPT connections are interchangeable with JIS tapered thread connections (interesting that the quote below says the JIS Tapered Pipe "has metric threads per JIS B 0203" yet they are "interchangeable" with Imperial BSPT connections--that somehow doesn't seem right):

JIS Tapered Pipe (PT) has metric threads per JIS B 0203. These are JIS tapered threads and are comparable to the design of BSPT fitting connections in their dimensions and appearance. JIS tapered thread connections are interchangeable with BSPT connections.

I'll try finding a BSPT JIS Tapered Pipe pitch gauge though. That may help solve part of this mystery.
 

2mbb

SILVER Star
Joined
Sep 1, 2003
Messages
5,662
Location
WC, CA
Yes that is interesting. I found what I think is an english copy of the JIS B 0203. In the table, thread pitch is described as "threads per 25.4mm". Consequently the thread pitch (distance between peaks) needs to be measured to four decimal places. 19 TPI = 19 threads per 25.4mm = pitch 1.3368 mm.

It seems like the Japanese copied the British for their pipe thread standard.
 

Attachments

  • JIS_Taper_Pipe_Threads.pdf
    155.7 KB · Views: 22

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Yes that is interesting. I found what I think is an english copy of the JIS B 0203. In the table, thread pitch is described as "threads per 25.4mm". Consequently the thread pitch (distance between peaks) needs to be measured to four decimal places. 19 TPI = 19 threads per 25.4mm = pitch 1.3368 mm.

It seems like the Japanese copied the British for their pipe thread standard.
Wow, excellent piece of history here. Thank you for sharing this. I might be able to take this to a specialty bolt place nearby that has measuring instruments and see if they can use this information to classify the screw plug for me. I think we are narrowing it down! I appreciate everyone's help. Thank you!
 

ToyotaMatt

Factory Focus-Point Mind-Set Approach
Supporting Vendor
GOLD Star
Joined
Aug 12, 2007
Messages
22,569
Location
EAST COAST
Website
vintageteqparts.com
Hello fellow MUDders, I am putting together a 2F for my 60 with scraped up parts and have a question about the 2F intake manifold's taper screw plug, pictured here:


View attachment 2909454

A previous owner of the intake manifold I have crossthreaded the hole the taper screw plug goes into and I want to chase the threads with a thread chaser since the plug will only go in about halfway now.

I was wondering if anyone knew if this screw plug was BPST or NPT and its threads per inch? I measured with the caliper and it looks like its 41/64" in diameter:

View attachment 2909462View attachment 2909496

The threads did not match either the 1.25 metric or the 18 or 20 SAE threads on my thread gauge, and I don't have a BSPT/NPT thread gauge to confirm if the taper plug screw's tpi might be within either of those standards. It looks like BSPT has a 19 tpi standard but then it also comes in 1/4" per foot taper and 3/4" per foot taper and I wouldnt know how to determine the per foot taper of this taper screw plug.

Here is how the plug measures against 18 tpi on the SAE thread gauge leaf:
View attachment 2909503

And here is a photo of the crossthreads some other bonehead besides myself put into the intake that won't allow the plug to screw in but half-way:

View attachment 2909508

If anyone could help me with information about what this taper screw plug and hole's size is so I can chase the thread appropriately, I would be so grateful and willing to pay the customary MUD fee of beers. I am hesitant to continue putting more parts on the engine until I address this as I don't want to end up having to disassemble it to take the manifolds back to the machine shop.

Also, if anyone may know what the best thread sealer to use on this application might be, that would be awesome if shared with me as well. I imagine the intake has to have a good vacuum and thus all ports that should be sealed should seal airtight.

Thanks to all who take a moment to share their thoughts and wisdom.


Here is the engine in progress:

View attachment 2909513
That port would be fine as a Vacuum gauge port, providing you can find a appropriate fitting.

I'm not 100% on this either, but I did at one point look into if Toyota had a vacuum port that might fit that spot and came up with this:

90404-51010​

Union

But I never went ahead and ordered one to see if it was the right size.

You wanna be the tester ? ;) 🤷‍♀️

View attachment 2910009


me thinks these are the DROIDS you are looking for ...............


FCDBE1F9-004E-47C9-87ED-A9B40261E8DE.jpeg
3CCFF2D6-3D7D-422E-8A74-E20F96BBB3E2.jpeg
022BE2F8-262F-4EC6-A8D6-F84EFCC07090.jpeg
 
Last edited:

garfieldthecat

SILVER Star
Joined
Sep 24, 2020
Messages
154
Location
California
Those are the screwplugs @ToyotaMatt

Do you know what tap size I can use to re-thread the cross threaded threads in my manifold? I think the size for this application is 3/8"-19 in either JIS PT aka BSPT aka ISO R(or Rc)? Please see attachment below and previous JIS attachment posted by @2mbb for various sizes and name changes of this type of screw and threads over the years. I think a 3/8"-19 BSPT tap might work (I can't find a thread chaser in this size), although @Spike Strip also is brilliant in suggesting to just notch the old screw plug and use that as a chaser.

Thank you for letting me know you have the screw plugs too. I will see if I can cancel my stealership order for them. Do you also have the EGR gasket that goes on the intake manifold? I know if you do, it'd be Toyota as well.

Thanks
 

Attachments

  • ti-Article-JIS.pdf
    276.8 KB · Views: 21

ToyotaMatt

Factory Focus-Point Mind-Set Approach
Supporting Vendor
GOLD Star
Joined
Aug 12, 2007
Messages
22,569
Location
EAST COAST
Website
vintageteqparts.com
Those are the screwplugs @ToyotaMatt

Do you know what tap size I can use to re-thread the cross threaded threads in my manifold? I think the size for this application is 3/8"-19 in either JIS PT aka BSPT aka ISO R(or Rc)? Please see attachment below and previous JIS attachment posted by @2mbb for various sizes and name changes of this type of screw and threads over the years. I think a 3/8"-19 BSPT tap might work (I can't find a thread chaser in this size), although @Spike Strip also is brilliant in suggesting to just notch the old screw plug and use that as a chaser.

Thank you for letting me know you have the screw plugs too. I will see if I can cancel my stealership order for them. Do you also have the EGR gasket that goes on the intake manifold? I know if you do, it'd be Toyota as well.

Thanks







1644025719023.png

1644025740282.png
 

Users who are viewing this thread

Top Bottom